U.S. Geological Survey Home AASG Logo USGS HOME CONTACT USGS SEARCH USGS
National Geologic Map Database

Geologic Unit: Chadron

Usage:

Chadron Formation (CO)
Chadron Formation of White River Group (CO*,MT*,NE*,ND*,SD*,WY*)


Subunits:

(alphabetical): Ahearn Member (SD), Beaver Divide Conglomerate Member (WY), Chalky Buttes Member (ND), Crazy Johnson Member (SD), Peanut Peak Member (SD), South Heart Member (ND).


Geologic age:

early Tertiary (late Eocene or early Oligocene)*


Type section, locality, area and/or origin of name:

Not designated. Named from exposures at Chadron, Dawes Co., NE (Darton, 1899, 1931).
Standard [Principal reference] section: in Big Badlands, south fork of Indian Creek, from sec. 34, T. 3 S., R. 12 E., to sec. 10, T. 4 S., R. 12 E., Pennington Co., SD (Clark, 1954).


AAPG geologic province:

Chadron arch*
Denver basin*
Williston basin*
Sioux uplift*
Wind River basin
Green River basin


For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.

Asterisk (*) indicates published by U.S. Geological Survey authors.

"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).

Slash (/) indicates name does not conform with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005). This may be explained within brackets ([ ]).